Bilbao injector beam commissioning Experiences During Hadron LINAC

Bilbao injector beam commissioning Experiences During Hadron LINAC Commissioning Madrid 25 -29 January 2021 Accelerator Division Team

- Introduction Experiments done so far. Summary

ESS main contributions MEBT RF SYSTEMS Our main contribution to ESS accelerator, the MEBT, was completed on late 2019. 2020 was dedicated to installation, hardware tests, and RF conditioning. Hopefully 2021 will be the year of the commissioning The RF equipment in the commissioning phase. The contribution will be completed by mid 2021. TARGET MIRACLES The Target in kind contribution will be completed in 2020 -2021. The TBD was delivered to ESS on January 2020. Monolith vessel production is completed and it was deliver to ESS on October 2020. Target system is on manufacturing phase, it will be deliver to ESS on early 2021. The main contribution to ESS Instruments is MIRACLES (To. F-BS spectrometer). MIRACLES is in its Detailed Design Phase (CDRs in 2021). In parallel to the design activities, Early Procurement & Manufacturing for some components is on going.

In-house Project RF [Completed] ION SOURCE H+ 45 ke. V [Completed] LEBT 2 solenoids [Completed]* RFQ 3 Me. V[On going] MEBT DELIVERED! [Completed] MEBT

Commissioning Main Objective 75 ke. V --> 45 ke. V 3 Me. V 0. 25 π. mm. mrad 800 mm shorter! – A RFQ has been design and approved by TAC evaluation report. – This design results in a shorter (3. 2 m) and more efficient RFQ. – If vacuum tests are successful, brazing stage could be avoided. – From 45 ke. V to 3 Me. V – Total length of 3. 12 m (4 segments) – Uniform 85 k. V inter-vane voltage – RFQ tuning system is based on water cooling system.

RF Control Room Small Labs RFTX LEBT ACC. Control Room ECR Ion Source 45 ke. V/40 m. A

Ion Source characteristics: – ECR type source located on HV platform ( 45 k. V) – Frequency: 2. 7 GHz – Tunable magnetic field provided by 4 coils, independently powered – 4 electrode extraction system (PE, Puller, Repeller, Ground ) – PE, Puller and Repeller can be moved in order to optimize the beam focusing in terms of extraction voltage, plasma parameters and beam currents ISHP Status IE voltage 45 -50 k. V Pulse width 0. 4 -3. 5 ms Pulse repetition rate 1 -40 Hz Itot 35 m. A Plasma ϕ 7. 5 mm

RFQ - In-house Design, taking aspects from ISIS-FETS RFQ and Linac-4 Overall: A unique RFQ different from others. - Fabrication started on 2016 (first segment). - Segment 1 tests performed: Metrology, vacuum, tuning, LPRF. These have confirmed designed choices. - Segments 2 -4 started January 2021.

Experience so far

LEBT STAGES STAGE #0 Ion source characterisation with first diagnostic vessel. No solenoids. STAGE #1 One solenoid, two diagnostics vessels before and after the solenoid. STAGE #2 Complete set-up: two solenoids, three diagnostics vessels before and after solenoid each solenoid.

STAGE 0: plasma optimization • Gain / Phase Detector • IQ demodulators • Power detectors RF power TUNERS 1 -3 Power supplies 4 -1 H 2

STAGE 0: V repeller effects Beam profile characterization depending on the repeller voltage – The suppression electrode also reduces X-ray radiation caused by back streaming secondary electrons that get accelerated and collide with the source. – Effect on the BN disk produced by back streamed electrons when suppressor electrode is OFF 2 ħω e- e-

STAGE 0 V repeller effects Beam profile characterization depending on the repeller voltage -1. 5 k. V – The function of the middle electrode between the two grounded electrodes is to inhibit the back-flow of electrons into the ion source from the downstream region. – This Accel-decel system —where positive hydrogen ions are accelerated in the first and decelerated in the second gap; preserves the space charge compensation of the extracted beam after this second. 0 k. V -1. 5 k. V 45 k. V 0 k. V

LEBT STAGES STAGE #0 Ion source characterisation with first diagnostic vessel. No solenoids. STAGE #1 One solenoid, two diagnostics vessels before and after the solenoid. STAGE #2 Complete set-up: two solenoids, three diagnostics vessels before and after solenoid each solenoid.

STAGE 1 overview COLLIMATOR Transmission Extraction gap optimised B and h/v Steering characterised h/v Beam Profile analysed Beam Specimen Kr Neutralisation studies h/v Emittance BEAM SHUTTER SOLENOID Scintillator Screen ACCT BIF WS Stage I ACCT WS Scintillator Screen EMU

STAGE 1 Commissioning ION SOURCE: extracted Beam Profile: – Extraction gap distance characterisation and beam core calibration – Beam profile characterisation –WS –Scintillator screen –Beam induced fluorescent – Specimen identification – Studies of Fringe field effects – Studies of Kr neutralisation effects

STAGE 1 Commissioning ION SOURCE: extracted Beam Profile: – Extraction gap distance characterisation and beam core calibration – Beam profile characterisation – WS – Scintillator screen – Beam induced fluorescent – Specimen identification – Studies of Fringe field effects – Studies of Kr neutralisation effects Family 5 Scintillator Screen Family 7

Compared to Plasma lab Scintillator Screen Family 5 Family 7 Flower - Extracted H+, H 2+, . . after extraction elected system - Scintillator Quartz employed to identify plasma configuration families. - Plasma shape is well preserved even after the 45 k. V electrode shape extraction system. Donut Ring - Electric probe system combined with time resolved acquisition of incoming, reflected power and light emission to measure typical breakdown and decay times in pulsed operation mode. - Ultra fast pictures were taken to identify various plasma distribution modes

STAGE 1 Commissioning ION SOURCE: extracted Beam Profile: – Extraction gap distance characterisation and beam core calibration – Beam profile characterization –WS –Scintillator screen –Beam induced fluorescent – Specimen identification – Studies of Fringe field effects – Studies of Kr neutralization effects 1 2 ACCT 1 ACCT 2 0. 065 0. 390 0. 13 0. 195 0. 260 0. 325. Solenoid (T) [1] Back streamed electrons are e- H+, H 2+ captured by SOLENOID Magnetic field [2] Over-focusing solenoid effect

STAGE 1 Commissioning ION SOURCE: extracted Beam Profile: – Extraction gap distance characterisation and beam code calibration – Beam profile characterisation –WS –Scintillator screen –Beam induced fluorescent – Specimen identification – Studies of Fringe field effects – Studies of Kr neutralisation effects PENCIL BEAM STEERER SCINTILLATOR SCREEN The third peak does not match to H 3+ other residuals?

STAGE 1 Limitations The employed field-maps have been measured by means of a triple-axis hall probe, mounted on a computer numerical control (CNC). Fringe fileds could not measured due to test bench limitation. Experimental characterization of the beam profiles for different solenoid magnetic configurations were stored. 150 A 0. 2 T IBSIMU+ TRACEWIN simulations employing accurate 3 D field-maps In the simulation, the geometrical parameters, foreseen collimation effects and measured field-maps are included.

STAGE 1 Emittance callibration EMITTANCE METER UNIT Beam Profile and emittance characterization for different solenoid configurations In order to prove that the employed algorithm lacks of any bias. A specific well known beam has been generated, and analysed by means of the data gathered with this virtual pepper-pot. The layout of this pepper pot is made of a 2 mm block of Cu (ø 2 mm) followed by a 0. 5 mm tungsten layer (ø 0. 1 mm) and finally collimated by a 10 mm long Cu block ø 2 mm. In all cases the 13× 13 grid is separated by 3 mm.

STAGE 1 Limitations Emittance EMITTANCE METER UNIT Beam Profile and emittance characterisation for different solenoid configurations 140 A 155 A Converging beam Diverging beam

STAGE 1 ESS test stand Successful Complete system integration tests in Bilbao integration in collaboration with ESS control and Diagnostics team. - Front End - Back End - Motion Control - µTCA IOx. OS Useful to - Fine tune grounding issues in Front end - Adjust Back End

Procedure pre-RFQ 1. Pencil beam 1. 2. 3. Centre beam in solenoid #1. Scan the beam in x & y. 2. Step the solenoid field. 3. Repeat the x/y scans. 4. Determine the x/y location where the solenoid no longer steers the beam Find the set-point of solenoid #1. 1. 4. Repeat procedure for solenoid #1 Find the set-point of solenoid #1. 1. 6. Scan the solenoid field and measure the emittance & transmission at each point. Centre beam in solenoid #2. 1. 5. Thread beam to the end of the LEBT. Use a beam collimator and roughly centre in the diagnostics. Using steerers. Repeat procedure for solenoid #2. Characterise the beam at the entrance on the RFQ. 1. Transmission ACCT 1 to ACCT 2. Twiss parameters. 3. Transversal emittance. 4. Measure build-up time of the space charge compensation. 5. Measure bunch length/ longitudinal shape. 6. Measure energy. 7. Measure energy spread. ACCT BIF WS FC WF RPA ACCT WS BIF Scintillator Screen EMU

On going improvements

On going Improvements FC in second vessel, cabled, integrated and tested with beam Second solenoid placed and cabled. The FC system has been integrated using a spare PXI. ± 1 k. V power supply is used to control the repeller voltage. Iris collector also measures current to understand the halo. The second solenoid has placed in the line to understand better the behaviour of the beam along the LEBT line. Power supplies upgrade, cabled, tested and integrated The new set of power supplies provide more robustness to the system the cage has been adapted to the new cabinet and getting ready for the future upgrades that will include the RFQ.

On going Improvements Control Integration improvements Automatization routines and archiving Deep learning techniques The on going EPICS integration, new GUIs and the improvements in the integration lead to more automatised runs that allow to control the system more efficiently Multi parameters scans required to understand better the machine. After a sufficient level of integration is achieved, pattern recognition, algorithms, multi parameter optimization, bayesian 4 D search routines can be applied to assist operators.

On going Improvements: New Coupler Different models studied to improve area below the curves in the Ez (z). Electric field map for a waveguide connected to the coupler N 11 and the to the plasma chamber. Improved Coupler design manufactured. A few parts missing before installation.

On going Improvements: RF amplifier

And for the next workshop… We are eager to show the experience with the ESS MEBT in 2021 !

Summary - Versatile and In house developed Ion source. Learning process experiment. - RFQ Segment 1 (aka proof of principle) finished and S 2 -S 4 machining on going. - Control integration improvements are essential for a better understanding of the physics. - Significant improvements on going on the Ion source and the LEBT. - Different suite of systems employed to understand the basic principles and performance of the ion source. - A lot of Practical experience gained to develop diagnostics and control systems for the ESS MEBT. MYRRHA, and FAIR projects